1. Field of the Invention
The present invention relates to an electromagnetically suspended floating floor apparatus, and particularly to an electromagnetically suspended structure which is spatially separated from beams and pillars of a building by magnetically suspending the floor to avoid vibration thereof.
2. Related Arts
Equipment such as an electromicroscope and a semiconductor manufacturing apparatus, which must be isolated from vibrations are usually mounted on a vibration eliminating apparatus when installed in a factory. A vibration eliminating apparatus using a magnetic suspending system, which has an excellent vibration eliminating capability has been developed, replacing a conventional apparatus utilizing pneumatic springs or rubber, and details of such vibration eliminating apparatus are given, for example, in Japanese Patent Laid-open No. 203040/92.
FIG. 1 illustrates an example of a conventional vibration eliminating apparatus using a magnetic suspending system. Equipment such as an electromicroscope or a semiconductor manufacturing apparatus which must be isolated from vibration (not illustrated) is mounted on a vibration eliminating table 1, which is maintained in a suspended state by means of an electromagnetic actuator 2. Therefore, even if the installation floor (not shown) on which the electromagnetic actuator 2 is installe,d is caused to vibrate by an earthquake or the like, no vibration is transmitted to the suspended vibration eliminating table 1, and therefore equipment which is installed on the table is not affected by the vibration of the installation floor.
FIG. 2 is an explicative diagram of an electromagnetic actuator 2 of the vibration eliminating apparatus illustrated in FIG. 1. On the vibration eliminating table 1, on which a machine may be mounted, is fixed a yoke 3 consisting of a magnetic material. Electromagnets 4 are fixed to the installation floor 6 and suspend the magnetic yoke 3 that is fixed to the vibration eliminating table 1 with a magnetic attracting force. A gap between a pole of the electromagnet 4 and the magnetic yoke 3 to be suspended, as a target, can be measured with a displacement sensor 5. A controller 7 comprises a compensation circuit 9 and a power amplifier 10 used to control an excitation current provided to the electromagnet 4 so that the vibration eliminating table 1 and the magnetic yoke 3 can be stably suspended in a target position on the basis of the output from the displacement sensor 5.
Since the vibration eliminating apparatus explained above is provided for each piece equipment that is sensitive to vibration, any change to the configuration of the equipment within the installation room requires changing the arrangement of the vibration eliminating apparatus. Such a change may entail modifying the building housing the equipment. Moreover, in a semiconductor manufacturing factory, for example, a problem occurs in that it is difficult to make modifications to change the arrangement of the vibration eliminating apparatuses since such facilities are often replaced due to rapid technical innovation.